High temperature creep behavior of a low alloy Mn-Mo-Ni reactor pressure vessel steel

Creep behavior of a low alloy Mn-Mo-Ni reactor pressure vessel steel received in post weld heat treatment condition has been studied in the temperature range of 600–900 °C. The steel exhibited three stage creep behavior. The steady or secondary creep rates for different stress conditions for a particular temperature were determined using stress change tests. Temperature change tests were conducted to determine the steady state creep rates at different temperatures at a particular stress. The creep rates obtained from different tests were analyzed using the Norton's and Bird-Mukherjee-Dorn creep equations to determine the stress exponent (n) and the creep activation energy (Q). The values of n and Q obtained signify dislocation climb as the underlying creep mechanism in steel. Electron back scatter diffraction (EBSD) study indicated formation of fine subgrain structure in the crept sample.